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Efficient Cells Cut the Cost of Solar Power

Sunday, 01 January 2012

NASA Technology

If you visit Glenn Research Center, you might
encounter a photovoltaic (PV) array that looks unlike
anything you’ve ever seen. In fact, what one would
normally identify as the panel is actually a series of curved
mirrors called solar concentrators, engineered to reflect
sunlight rather than absorb it.

These concentrators gather, intensify, and focus sun
beams upward, aiming at a fixture containing specialized
silicon concentrated PV chips—the actual solar cells. If
you stay by the array for a while, you’ll notice that the
solar concentrators follow the path of the sun throughout
the day, changing position to best capture and utilize the
sunlight.

The specialized chips that make the technology possible
are the brainchild of Bernard Sater, an engineer who
had worked at Glenn since the early 1960s before retiring
to pursue his unique ideas for harnessing solar power.
Sater contributed to multiple PV projects in the latter
part of his career at the Center, including research and
development on the International Space Station’s solar
arrays. In his spare time, he enjoyed tinkering with new
approaches to solar power—experiments that resulted in
the system installed at Glenn today.

Sater’s basic idea had two components. First, he
wanted to create a silicon cell that was smaller, more
efficient, and much lower cost than those available at the
time. To ensure that the potential of such a chip could
be realized, he also planned on pairing it with a system
that could concentrate sunlight and focus it directly on
the cell.

When he retired from Glenn in 1994 to focus on
researching and developing the technology full time, Sater
found that NASA was interested in the concept and ready
to provide funding, facilities, and expertise in order to
assist in its development.

Technology Transfer

Sater’s first set of Space Act Agreements with Glenn
resulted in the development of what is today the
PhotoVolt cell: a silicon chip many times smaller than
those employed in conventional solar technology—each
array of miniature cells is about the size of a thumb nail.
At the time, no standards existed to test high intensity
solar cells, so Sater worked with NASA scientists to
develop test methods in Glenn’s world-class facilities.

All the while, Sater’s progress was supported by his
son, Neil. Although Neil was employed at Intel at the
time, he worked with his father in his spare time to
develop the technology. With PhotoVolt in place, Neil
and Bernard became convinced that it was time to move
toward commercialization. Says Neil, “What we decided
in 2007, when I decided to go full time, is that we needed
to develop the whole solution. We had this chip, so next
we needed a concentrator that the chips could go in.”

The two formed Oberlin, Ohio-based GreenField Solar
Inc. and began assembling a team and raising money—
all while continuing to develop the technology under
ongoing Space Act Agreements with Glenn. Their solar
concentrator concept soon became the StarGen system,
which features parabolically shaped mirrors designed for
use with the PhotoVolt cell.

The partnership between Greenfield Solar and Glenn
has reaped rewards for both parties. NASA has received
access to the unique chip, which has played a role in multiple
space missions, and GreenField Solar has refined its
solar concentrator system. “The facilities and expertise at
Glenn have been essential to solving numerous technical
issues,” says Neil.

In 2008, Glenn purchased and installed two StarGen
solar concentrators for research and testing, as well as to demonstrate the cutting-edge solar technology at the
Cleveland facility. Roshanak Hakimzadeh, deputy chief
technologist at Glenn, points to GreenField Solar as an
example of how beneficial the Agency’s partnerships can
be for everyone involved. “GreenField Solar’s founders
were able to work closely with experts in the field at
Glenn, which contributed to the success of the company.
This technology represents a successful partnership
between NASA and the commercial sector.”

Benefits

Whereas conventional solar cells lay flat and passively
collect sunlight, the StarGen solar concentrators ensure
that the PhotoVolt cells receive as much intensified light
as possible, all day. Between the sunlight being intensified
by mirrors—hundreds of times stronger than normal—
and the efficiency of the PhotoVolt cell, Neil says that the
StarGen system is able to provide about 200 times more
power than conventional panels for a given amount of
silicon.

Bernard says it’s the smaller size of the PhotoVolt cell
that reduces costs and gives GreenField Solar its competitive
edge. “The majority of the market is large panels of
silicon. The problem is that silicon is relatively expensive,
especially compared to glass. So we take all of that silicon
and shrink it down to just a little chip, and then we concentrate
the light so that we produce more power using
much less silicon.”

The intensity of the system produces an excess of
thermal energy, which Neil says can be put to creative
secondary uses. At Glenn, for example, NASA originally
planned on using that energy to heat a nearby conference
room. And currently on another site, a greenhouse
stationed next to the panels is being kept warm with the
superfluous heat.

Solar power may be a renewable, clean, zero-emission
energy source, but it still occupies only a small portion of
the total market for energy. Neil sees GreenField Solar’s
technology as having the potential to change that in the
long run by making solar power less expensive even than
fossil fuels and nuclear power. “Our mission is to move
solar into mainstream deployment. When you drive
around, you rarely see solar panels—in fact, you really
notice them when you see them, because they’re so rare.
We want to make them ubiquitous.”

After spending many years developing the technology,
in large part through its partnership with NASA,
GreenField Solar is now making its system commercially
available in 2012. The company is also focusing globally,
with strong connections in Asia. While the technology
itself was developed by the company, Neil emphasizes that
NASA’s support was essential to their success in bringing
it to the point of commercialization.

“Right now we have 30 employees, and it’ll be a lot
higher in the future,” he says. “Essentially, these jobs exist
because of NASA’s investment in this technology. We
wouldn’t have been able to raise the funds we’ve raised
or position ourselves the way we have without NASA’s
support.”

Question of the Week

This week's Question: A recent study created by the Arizona-based Paragon Space Development Corporation says its life support system could help humans survive on Mars. The proposed Environmental Control and Life Support System, the company says,...